Before the appearance of the first oral treatment, male sexual impotence was treated by means of intracavernous injections and other methods, due to, in particular, innumerous concerns on the adverse reactions that oral route administration would be able to cause in humans. Papaverine and pentoxifylline, for example, were used in the treatment of erectile dysfunction by intracavernous injections. Other methods of treatment, less efficient, were, for example, psychological therapies and surgical implants.
The treatment by oral route is more acceptable by man and it emerged from clinical studies using specific inhibitors to cGMP, PDE, and more specifically, PDE-5. The predecessor of these compounds was 5-[2-Ethoxy-5-(4-methylpiperazinylsulphonyl)phenyl]-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazol[4,3-d]pyrimidin-7-one, or sildenafil, with vasodilator properties and potentiator properties of Endothelium Derived Relaxing Factor (EDRF) and nitrovasodilators. Sildenafil is the active principle of the medicament Viagra®.
Later, other PDE-5 inhibitor compounds were developed and described in various publications of specialized literature, and in patent publications. The most well-known are vardenafil, the active principle of the medicament Levitra®, and tadalafil, the active principle of the medicament Cialis®.
Another class of PDE-5 inhibitor compounds is described in the publication WO 03/000691. Therein are disclosed a series of compounds derived from β-carboline, which are prepared from compounds of formula (a) and (b) below, disclosed, respectively, in U.S. Pat. Nos. 6,117,881 and 5,859,006.

The compounds of the present invention, derivatives of 2-(3-methylenedioxy)-benzoyl indol, can be utilized in treatment of sexual dysfunction, and in one embodiment, can be utilized as stimulators of NO expression in tissues, and in another embodiment, can be utilized as selective inhibitors of the enzyme phosphodiesterase, in particular phosphodiesterase type 5 (PDE-5).